%20 is, for HTML identifiers and links, hexadecimal 20, which is decimal 32, which is the space character (" ") in ASCII.

"Tutoring.aspx%20" is the same as "Tutoring.aspx " as far as the web server is concerned. And it very well may not be the same as "Tutoring.aspx" [although a web server might drop the trailing white-space ... the problem is that when you *explicitly append that %20, it sort of signals to the web server *not* to drop that last space character ...]